5.5 Switching Characteristics

Input tt = 6ns. Unless otherwise specified, CL = 50pF

PARAMETER

VCC (V)

25°C

-40°C to

85°C

-55°C to

125°C

UNIT

TYP

MAX

MAX

MAX

HC TYPES

tpd

Select to outputs

2

245

305

370

ns

4.5

21(1)

49

61

74

6

42

52

63

tpd

Data to outputs

2

175

220

265

ns

4.5

12(1)

35

44

53

6

30

37

45

tpd

Enable to high Z and enable from high Z

2

140

175

210

ns

4.5

11(1)

28

35

42

6

24

30

36

tt

Output transition times

2

75

95

110

ns

4.5

15

19

22

6

13

16

19

Ci

Input capacitance

10

10

10

pF

CO

Three-state output capacitance

15

15

15

pF

Cpd (3) (4)

Power dissipation capacitance

5

60(2)

pF

HCT TYPES

tpd

Select to outputs

4.5

18(1)

42

53

63

ns

tpd

Data to outputs

4.5

12(1)

35

44

53

ns

tpd

Enable to high Z and enable from high Z

4.5

12(1)

30

38

45

ns

tt

Output transition times

4.5

15

19

22

ns

Ci

Input capacitance

10

10

10

pF

Cpd (3) (4)

Power dissipation capacitance

5

60(2)

pF

(1)

Typical value tested at 5V, CL = 15pF.

(2)

Typical value tested at 5V.

(3)

CPD is used to determine the dynamic power consumption, per channel.

(4)

PD = VCC 2fi(CPD + CL) where fi = input frequency, CL = output load capacitance, VCC = supply voltage.

CD54HC251, CD74HC251, CD54HCT251, CD74HCT251

SCHS169D – NOVEMBER 1998 – REVISED MARCH 2022

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